In a plant in which asphalt concrete mix is prepared, the hot asphalt mix is temporarily stored in a thermally insulated silo-like storage bin so that it can be hauled to the site of use as and when it is needed, independently of the rate at which it is mixed. The storage bin has a bottom outlet and is elevated high enough above ground level so that trucks can be driven under it to be loaded by gravity flow. The inlet to the storage bin is at its top, and therefore the freshly prepared asphalt mix must be carried up to the storage bin inlet by means of an elevator.
In older asphalt mix plants the elevator used for filling the storage bin was usually an inclined slat conveyor, but most plants constructed during the past several years have had a bucket elevator which extends straight up alongside the storage bin and which occupies less space than a slat conveyor.
A bucket elevator comprises a drive chain or similar endless carrier to which buckets are fastened at intervals. The carrier is trained around sprockets that drive it and dispose it in a pair of vertical stretches, along one of which the buckets move downwardly and along the other of which they move upwardly. In the bottom portion of their orbit the buckets pass through a charging bin in which they scoop up asphalt mix that is to be carried up to the storage bin inlet. The charging bin, which is also known as the "boot" of the bucket elevator, receives asphalt mix directly from the pug mill or drum mixer in which it is mixed.
One disadvantage of a bucket elevator is that its charging bin must be cleaned out to some extent at the end of each day's operations, when the bucket elevator is shut down. Hardened asphalt mix in contact with the buckets and/or the endless carrier would strongly resist movement of those parts upon restarting of the bucket elevator and could damage or destroy the chain, the buckets, the bottom sprocket assembly, or even the power train that drives the elevator. To ensure free movement of the bucket elevator parts upon restarting, all material has to be removed from between the buckets and the side walls of the charging bin. The bottom of the charging bin need not be cleaned out completely, but a substantial amount of mix must be removed from beneath the buckets because the chain tension take-ups on a bucket elevator are on its lower portion, and any material left in the bin should be clear of the lowermost buckets and the chain portion that carries them in the event they move down to their lowest level.
Heretofore such clean-out of the charging bin has been done manually, with shovels, through clean-out doors in its bottom. Although manual clean-out was difficult, unpleasant and time consuming, the use of any type of mechanized scoop (front end loader or the like) seemed to be out of the question because of the confined spaces from which the mix had to be removed.
Because manual clean-out is onerous work, it has not always been done at the end of every operating day, and the consequences of the failure or neglect were usually costly.
The object of the present invention is to provide simple and inexpensive automatic means in asphalt mix storage apparatus for preventing asphalt mix in the charging bin from interfering with operation of the carrier and buckets of the bucket elevator when that elevator is restarted after being shut down long enough for the asphalt mix to harden.
More specifically, it is an object of this invention to provide simple and effective automatic means for removing asphalt mix from the bottom portion of the charging bin and shifting the removed mix to a location from which it can be readily picked up by an end loader or the like, so that manual shoveling of asphalt mix out of the charging bin is unnecessary.
Thus an ultimate object of the invention is to eliminate an important cause of difficulties, malfunctions and breakdowns in bucket elevators associated with asphalt mix storage apparatus, while at the same time eliminating the need for laborious, unpleasant and time-consuming manual clean-out of the charging bin of such an elevator after each daily shut-down.